Belt conveyor drier for web material



y 14, 1964 E. J. JUSTUS 3,140,930

BELT CONVEYOR DRIER FOR WEB MATERIAL Filed July 20, 1961 4/: 002' 4/! 0v4/: ml 4/: 007

I v & g L [/35 /0 6 Z 2 mmvron.

United States Patent 3,140,930 BELT CONVEYOR DRIER FOR WEB MATERIALEdgar J. Justus, Beloit, Wis., assignor to Beloit iron Works, Beloit,Wis, a corporation of Wisconsin Filed July 29, 1961, Ser. No. 125,405 9Claims. (Cl. 34-456) The present invention relates to an improvedmechanism and method for drying a moving paper web after it has left theforming section of a paper making machine.

In the usual paper machine dryer section, there are provided dryer drumssuch as a Yankee dryer or conventional dryer drums, each of which arecylindrical in shape and have heated outer cylindrical surfaces forcarrying the paper web and heating it causing an evaporation of themoisture from the web. The paper web is first formed in the formingsection by the deposit of a suspension of paper fibers on a forarninoussurface and dewatering the fibers to form a web. After this formingsection the traveling web passes to a dryer section which may firstinclude other drying means such as press felts and which usuallyincludes heated dryer drums as above described. The dryer drumsnecessitate the provision of bulky equipment requiring thermal energysuch as provided by steam and require withdrawal of the condensate ifsteam is used. The rate of drying of the web is de pendent upon the rateof evaporation of water and this in turn is dependent upon the abilityof the mechanism to transfer heat energy to the web and to remove themoisture bearing air for increasing evaporation rate. The rate of heattransfer is dependent upon the surface area of the drums in contact withthe web. The drums have usually been arranged in a pattern so that thepaper passes over their surfaces in a serpentine path inasmuch as itmust be held in contact with the surfaces.

It is an object of the present invention to provide an improved methodand mechanism for evaporating moisture from a paper web in a dryingsection of a paper making machine which makes possible the more rapidtransfer of thermal energy to the moisture in the web to therebyincrease the rate of evaporation and drying rate.

A further object of the invention is to provide a paper web dryer whichmakes possible the exposure of a greater area of the Web to a heatingmeans in proportion to the volume of equipment required and therebyincreases the rate of evaporation of water for a given machine space.

A still further object of the invention is to provide a drying mechanismwhich avoids the build-up of a layer of air at the surface of the webwhich is saturated with water vapor or at a high relative humidity whichheretofore reduced the drying rate.

A further object of the invention is to provide an improved mechanismfor a drying section of a paper machine which eliminates the need forheavy cast iron drying drums, which effects a saving in cost ofconstruction and cost of operation, which obtains more uniform dryingacross the web, which eliminates the need for high pressure steam supplylines and condensate removal lines, and which is generally moreefficient and effective.

As a feature of the invention, the method and mechanism contemplaterunning a web of paper or board through a dryer section of a papermachine which is constructed so that the web is held against surfacesarranged to provide a greater drying area than heretofore available. Thedryer section includes provision of a forarninous surface for supportingthe paper web with means for providing a pressure differential acrossthe web such as by applying a suction beneath the forarninous surface,and providing a supply of heated air to the exposed surface of thesupported web, which may be confined to the area by providing anenclosure or hood facing the outer surface of the supported area. Noheated air passes through ice the web and the suction is utilized solelyto hold the web to the supporting surface which can be arranged in aunique path for maximum heat transfer to the web. It has heretofore beennecessary to arrange the drying path giving concern to holding the highspeed traveling web on the drying rolls, and with heat transfer limitedto time of contact with the cylindrical roll surfaces. Heat energy istransmitted to the moisture in the web by the heated air and a layer ofsaturated air is prevented from building upon the web surface by themoving warm air above the web. The suction holds the web to theforaminous surface permitting the use of long runs of supported Webarea.

Other objects, advantages and features will become more apparent withthe teaching of the principles of the invention in connection with thedisclosure of the preferred embodiments thereof in the specification,claims and drawings, in which:

FIGURE 1 is a diagrammatic showing of a drying section of a papermachine constructed in accordance with the principles of the presentinvention; and

FIGURE 2 is a schematic diagram showing the sequence of several sectionsof a paper making machine.

As shown on the drawings:

As illustrated in FIGURE 2, in a paper making machine a paper web isformed in a forming section 9 which has a forarninous surface fordewatering a suspension of paper fibers supplied at 8. The formed paperweb travels into a drying section 10 and on to further sections of themachine where the paper may be finished and may be handled such as bybeing slit and wound. These sections of the machine are fullyappreciated by those skilled in the art and need not be described indetail.

The instant invention pertains to an improved portion of the dryingsection 10 in which water is taken from the Web of paper or board byevaporation from the surface of the web and it will be understood thatthe drying meth- 0d and mechanism may be provided as a part of thedrying section, or in addition to other drying mechanisms but is welladapted to replacing devices such as dryer drums which take up morespace and require more bulky heavier equipment. For example, the dryingsection 10 may include first water removing mechanism at 10a such asdrying felts, and second mechanism at 1012 such as the mechanism shownin FIGURE 1.

In the arrangement shown in FIGURE 1, the web W, which is a paper webcontaining moisture and travelling through a paper making machine, iscarried through a serpentine path on forarninous support surfaces whichare in the form of Wires or belts carried on suction rolls. Suctionrolls are provided at 22, 23, 24, 25, 26 and 27 and the web leaves thedryer section shown over a guide roll 28.

A first belt 29 is supported on the suction rolls 22 and 23, a secondbelt 30 is supported on the suction rolls 24- and 25 and a third belt 31is supported on the suction rolls 26 and 27. The belts may be drivensuch as by driving the suction rolls through suitable drives, not shown,or may be driven through engagement with the moving web, and the beltsurfaces move at the surface speed of the moving web.

Each of the suction rolls has a forarninous outer surface and isconnected to means for applying a suction to the interior thereof. Themechanism for applying a suction may be of various types which will befully appreciated by those skilled in the art and need not be describedin detail. The letter S indicates suction within the rolls such as maybe applied by a vacuum pump indicated at P. The belts or wires are alsoforarninous so that the space within them is subjected to the suctionand so that the web W carried on the surface thereof will be subjectedto the suction on its lower surface and a pressure dilferential willexist across the web. The suction is for supporting the web on the flatsurfaces permitting high speed travel of the webs, with a reversal oftheir direction of travel without losing control of the web. The web isnon-porous with respect to the air and a suction is applied to hold theweb on the surface with no flow of air through the web. A suction whichwould cause any appreciable penetration of the paper or board by the airwould effect a disruption of fibers or tearing of the web.

The exposed surface or outer surface of the Web opposite the surfacesupported by the belts is substantially at atmospheric pressure and issupplied with an atmosphere of heated air by hot air hoods or enclosingcaps 32, 34 and 35 and the hoods are shaped so that they form anenclosure to extend over the exposed surfaces of the Web at the areaswhere the other surface is supported by the foraminous belts.

Thus for its run through the dryer section shown in FIGURE 1, onesurface of the web is first subjected to a vacuum while the othersurface is subjected to a hot air atmosphere for a portion of its run,and the environment is then reversed. Referring to the surface of theweb W, first exposed to the hot air hood 32 as the outer surface, andthe surface I, first exposed to the vacuum of the belt 29 as the innersurface, the outer surface 0 when it reaches the suction roll 24 becomesexposed to the suction of the belt 30 and the inner surface I becomesexposed to the heated air supplied by the hood 34. A shield or seal 37is positioned at the location where the belt 29 runs onto the suctionroll 22 so that the Web will be smoothly transferred to the belt 30. Thesuction roll 22 is provided With an arcuate inner shielding seal 36 toprevent leakage of air into the roll. The roll 24 is similarly providedwith a shielding seal 38 on its inner surface to prevent leakage of airinto the interior of the roll 24 along its upper surface. The shield 38extends so that as the Web passes the shield 37 it will become exposedto the vacuum within the belt 30 and roll 24 to smooth the transfer tothe belt 30.

The web is supported on the belt 30 and is thereafter smoothlytransferred to the belt 31 and a seal 39 within the belt 30 effects asmooth transfer. Suction roll 27 is provided with a shielding seal 40 toprevent the leakage of air and the web smoothly leaves the belt 31 totravel onto the guide roll 28. While on the belt 31, the outer surface 0of the web W is subjected to an atmosphere of hot air by the hood 35 andthe inner surface subjected to suction. Hot air is supplied to the hoods32, 34 and 35 by suitable air supply mechanism shown schematically bythe arrows labelled Air In, and the moisture carrying air leaves asindicated schematically by the arrows labelled Air Out. The interior ofthe hoods may be kept at atmos pheric pressure or at slightly less thanatmospheric pressure to prevent escape of heated air and the edges ofthe hoods are close to the surface of the moving foraminous belts toprevent escape of air into the room. The air can be heated beforeentering the hoods or heated within the hoods.

In other words, the first, second and third belts provide a serpentinepath with the first belt providing a first surface 2a receiving the web,and reversing over the roll 23 provides a second surface 2%. The secondbelt 36 provides a continuation second surface 39a which extends in thesame direction as the second surface 291) of the first belt andsubstantially forms a continuation thereof. The surface 36!) of thesecond belt provides a third surface in the opposite direction of thesecond surface 30a and the surface 31a of the third belt provides acontinuation third surface which is a continuation of the third surface39b extending in substantially the same direction. This provides for asmooth transfer of the web and a reversal of its path and also areversal of the surfaces which are exposed to heated air and vacuum, andis repeated through the dryer section. It will be appreciated l thatadditional rolls and belts may be provided to obtain the drying areanecessary and that the position of the rolls and belts may be changed tobe horizontal, instead of vertical as shown.

In operation, the web W in FIGURES 1 or 2 arrives from the formingsection 9, FIGURE 2, at the drying section 10, and the mechanism ofFIGURES 1 and 2 provides at least a part of the drying section. The webis supported alternately on its inner and outer surfaces on a foraminoussurface provided by the suction rolls 22-27 of FIGURE 1, or by theforaminous belts 29, 30 and 31 of FIGURE 1. One surface of the web issupported on the foraminous surface and subjected to a vacuum whichholds the web on the surface, and the other exposed surface of the webis subjected to a flow of hot air from hood to transfer thermal energyand increase the temperature of the moisture in the web for evaporation,and the air will flow out of the hoods after flowing over the web andwill carry away evaporating moisture. The hood is close to the web atits sides but not sealed thereto.

It is contemplated that the belts may be of varying lengths, and asuflicient number of belts will be employed in sequence to effect thedrying necessary. It is further contemplated as being within the scopeof the invention that the belts provided a preferred form of foraminoussupport, the surfaces do not have to be straight and surfaces of othertypes such as cylinders may be employed.

Thus it will be seen that I have provided an improved unique mechanismand method for the drying section of a paper making machine which meetsthe objectives and advantages above set forth. The mechanism can beconstructed without the bulk of heavy cast iron drying rolls and willrequire reduced machine volume and will obtain rapid moistureevaporation from the paper web.

The drawings and specification present a detailed disclosure of thepreferred embodiments of the invention, and it is to be understood thatthe invention is not limited to the specific forms disclosed, but coversall modifications, changes and alternative constructions and methodsfalling within the scope of the principles taught by the invention.

I claim as my invention:

1. In a paper machine dryer section for drying a paper web, first andsecond closed loops of foraminous flexible belts, first and second pairsof spaced support rolls respectively within said first and second beltwith the rolls for each belt spaced apart for carrying the belt andforming linear runs therebetween, said runs extending substantiallyparallel to each other, said runs defining a paper web supporting pathextending sequentially over the first and second runs of the first beltand thereafter over the first and second runs of the second belt, saidbelts positioned close together so that the second run of the first belttravels toward the first run of the second belt and in the samedirection and has a delivery end spaced close to a receiving end of thefirst run of the second belt to transfer the web from the first to thesecond belt at the end of the second run of the first belt, means forcreating a suction within said belts along said runs to hold the Webthereon, a first U-shaped hood position over the first belt and havingsides extending along said first and second runs, a second U-shaped hoodextending over said second belt with the sides extending along saidfirst and second runs said hoods extending over the ends of the beltsbetween said first and second runs, means for directing a flow of heatedair from the first hood onto the first belt, and means for directing aflow of heated air from the second hood onto the second belt.

2. In a paper machine dryer section for drying a paper web, first andsecond closed loops of foraminous flexible belts, first and second pairsof spaced support rolls respectively within said first and second beltswith the rolls for each belt spaced apart vertically for carrying thebelt and forming vertical linear runs therebetween, said runs extendingsubstantially parallel to each other, said runs defining a paper websupporting path extending sequentially over the first and second runs ofthe first belt and thereafter over the first and second runs of thesecond belt, said runs positioned close together so that the second runof the first belt travels toward the first run of the second belt and inthe same direction and is close thereto to transfer the web from thefirst to the second belt at the end of the second run of the first belt,means for creating a suction within said belt to hold the web thereon,and a heated air source on the exposed surface of the web on said runsand over the end of the belts between the first and second runs forevaporating moisture from the web.

3. In a paper machine dryer section for drying a Wet paper web, first,second and third closed loops of foraminous flexible belts, a first pairof vertically spaced support rolls for the first looped belt definingfirst and second linear runs for carrying the paper web, a second pairof vertically spaced support rolls supporting said second loop definingfirst and second linear runs between them With said first run of saidsecond belt positioned to receive the web from said second run of thefirst belt and being closely spaced thereto and traveling in the samedirection, a third pair of vertically spaced support rolls for the thirdlooped belt defining first and second linear Web supporting runs betweenthem with the first run of the third belt positioned to receive the webfrom the second run of the second belt and being closely spaced theretoand traveling in the same direction, said web transferring from thefirst to the second belt and from the second to the third belt at theend of said second runs, means for applying a suction within each of theloops of said belts for holding the web on said runs, and a heated airsource on the exposed surface of the web over said first and said secondruns and over the end of the belt loop therebetween evaporating moisturefrom the web.

4. In a paper machine dryer section for drying a paper web, first andsecond closed loops of foraminous flexible belts, first and second pairsof spaced support rolls respectively within said first and second beltswith the rolls for each belt spaced apart for carrying the belt andforming linear runs therebetween, said runs extending substantiallyparallel to each other, said runs defining a paper web supporting pathextending sequentially over the first and second runs of the first beltand thereafter over the first and second runs of the second belt, saidbelts posi tioned close together so that the second run of the firstbelt travels toward the first run of the second belt and has a deliveryend spaced close to a receiving end of the first run of the second beltto transfer the web from the first to the second belt and said secondrun of the first belt and first run of the second belt traveling in thesame direction, said web transferring from the first to the second beltat the end of the second run of the first belt, means for creating apressure differential across said belts along said runs to hold the webthereon, and a heated air source on the exposed surface of the web onsaid first and second runs and over the end of the belts between theruns for evaporating moisture from the web.

5. In a paper machine dryer section for drying a paper web, first andsecond closed loops of foraminous flexible belts, first and second pairsof spaced support rolls respectively within said first and second beltswith the rolls for each belt spaced apart for carrying the belt andforming linear runs therebetween, said runs extending substantiallyparallel to each other, said runs defining a paper web supporting pathextending sequentially over the first and second runs of the first beltand thereafter over the first and second runs of the second belt, saidbelts positioned close together so that the second run of the first belttravels toward the first run of the second belt to transfer the web fromthe first to the second belt at the end of the second run of the firstbelt, said second run of the first belt and first run of the second belttraveling in the same direction, means for creating a suction Withineach of said belts for holding the web on the outer surface of the beltson said runs, and a heated air source on the exposed surface of the webon said first and second runs and over the end of the belts therebetweenfor evaporating moisture from the web.

6. In a paper machine dryer section for drying a paper web, first andsecond closed loops of foraminous flexible belts, pairs of spacedsupport rolls respectively within said first and second belts with eachpair having first and second rolls spaced apart for carrying the beltand forming linear runs therebetween, said runs extending substantiallyparallel to each other, said runs defining a paper web supporting pathextending sequentially over the first and second runs of the'first beltand thereafter over the first and second runs of the second belt, saidfirst run extending from the first to the second roll, said second runextending from the second to the first roll, said belts positioned closetogether so that the second run of the first belt travels toward thefirst run of the second belt and in the same direction to transfer theweb from the first to the second belt at the end of the second run ofthe first belt, said second rolls each being foraminous, means forcreating a suction within said belts and within said second rolls forholding the web to the belts and to the second rolls as the web passesfrom the first to the second runs, and a heated air source on theexposed surface of the web on said first and second runs and over theends of the belts between the first and second runs for evaporatingmoisture for the web.

7. In a paper machine dryer section for drying a paper web, first andsecond closed loops of foraminous flexible belts, first and second pairsof spaced support rolls respectively within said first and second beltswith the rolls for each belt spaced apart for carrying the belt andforming linear runs therebetween, each pair of rolls including first andsecond rolls with the first run extending from the first to the secondroll and the second run extending from the second to the first roll,said runs extending substantially parallel to each other, said runsdefining a paper web supporting path extending sequentially over thefirst and second runs of the first belt and thereafter over the firstand second runs of the second belt, said belts positioned close togetherso that the second run of the first belt travels toward the first run ofthe second belt and in the same direction to transfer the web from thefirst to the second belt at the end of the second run, said second rollseach being foraminous, means for creating a suction within said beltsand within said second rolls for holding the webs to the belts and tothe second rolls as the web passes from the first to the second runs,U-shaped air hoods projecting over said belts on said first and secondruns and over the belts on said second rolls between the first andsecond runs, and means for circulating heated air through said hoodsover the exposed surface of the moving web.

8. In a paper machine dryer section for drying a paper Web, first andsecond closed loops of foraminous flexible belts, first and second pairsof spaced support rolls respectively within said first and second beltswith the rolls for each belt spaced apart for carrying the belt andforming linear runs therebetween, said runs extending substantiallyparallel to each other, said runs defining a paper Web supporting pathextending sequentially over the first and second runs of the first beltand thereafter over the first and second runs of the second belt, saidbelts positioned close together so that the second run of the first belttravels toward the first run of the second belt and in the samedirection to transfer the web from the first to the second belt at theend of the second run, means for creating a suction within said beltsfor holding the web to the belt, and means for creating a flow of heatedair over the exposed web of the paper along said first and second runsand over the end of the belts between said first and second runs atsufficiently low pressure so that the air does not penetrate the Web.

9. In a paper machine dryer section for drying a paper 1 web, a closedlooped foraminous flexible belt, first and second spaced support rollsfor the looped belt defining first and second linear runs between them,means for creating a pressure differential across said belt to hold theweb on said runs, means for holding the Web on said belt as it travelsaround the second support roll from the first to the second run, webcarrying means traveling in the same direction as the second runpositioned immediately adjacent the end of the second run and receivingthe web from said second run at the end of the second run, and a heatedair source on the exposed surface of the web along said first and secondruns and over the end of the belts between said first and second runsevaporating moisture from the web.

References Cited in the file of this patent UNITED STATES PATENTS1,701,878 Freegard Feb. 12, 1929 1,996,020 Hurxthal Mar. 26, 19352,091,805 Chuse Aug. 31, 1937 2,760,410 Gillis Aug. 28, 1956 2,981,007Fleissner Apr. 25, 1961 FOREIGN PATENTS 1,104,438 Germany Apr. 6, 1961

1. IN A PAPER MACHINE DRYER SECTION FOR DRYING A PAPER WEB, FIRST ANDSECOND CLOSED LOOPS OF FORAMINOUS FLEXIBLE BELTS, FIRST AND SECOND PAIRSOF SPACED SUPPORT ROLLS RESPECTIVELY WITHIN SAID FIRST AND SECOND BELTWITH THE ROLLS FOR EACH BELT SPACED APART FOR CARRYING THE BELT ANDFORMING LINEAR RUNS THEREBETWEEN, SAID RUNS EXTENDING SUBSTANTIALLYPARALLEL TO EACH OTHER, SAID RUNS DEFINING A PAPER WEB SUPPORTING PATHEXTENDING SEQUENTIALLY OVER THE FIRST AND SECOND RUNS OF THE FIRST BELTAND THEREAFTER OVER THE FIRST AND SECOND RUNS OF THE SECOND BELT, SAIDBELTS POSITIONED CLOSE TOGETHER SO THAT THE SECOND RUN OF THE FIRST BELTTRAVELS TOWARD THE FIRST RUN OF THE SECOND BELT AND IN THE SAMEDIRECTION AND HAS A DELIVERY END SPACED CLOSE TO A RECEIVING END OF THEFIRST RUN OF THE SECOND BELT TO TRANSFER THE WEB FROM THE FIRST TO THESECOND BELT AT THE END